Thoughts on the Incra I-Box Box Joint Jig

[Mike Manning]

I'm supposed to look at an Incra I-Box box joint jig this evening. For those of you who own it or have used this jig extensively would you recommend it? What are the positives and probably more importantly what are it's drawbacks (beyond initial cost). As always, I appreciate the feedback from everyone!

Thanks, Mike

[Joe Bradshaw]

Mike, I bought one a few years back and have enjoyed using it. It is a bit fiddly to set up, but, once you have done that you can cut perfect box joints all day long. I purchased a DeWalt jobsite tablesaw and leave it set up full time. I tried it on my router table but did not have good luck with that. I use the Freud boxojoint blade set.
Joe

[daryl moses]

I purchased one a couple of years ago to make jewelry boxes. I seldom use it but once set up it works great.

[Charles Lent]

The I-Box jig is easy to set up for either a table saw or router table, if they have the industry standard 3/8 X 3/4 miter slot. There are adjustments to remove any side play, which is very important for accurate box joints, but the miter slot needs to be pretty close to the standard size for these adjustments to work. Setting the jig for a given size box joint is easy and very accurate, which is what makes this jig much nicer than any other on the market. You turn one knob to move the pin fingers over until the pin nearest the blade just kisses the blade. Then you turn the other knob to spread the fingers to the width of the cuts that you want, As you do this the jig is automatically setting the pin width. When set, turn the knob on the top of the I-Box to lock the settings. You should be done with the I-Box calibration. Make a test cut to be sure of the pin width and spacing, or a do test joint to be sure that a whole joint fits together well and you are. ready to go. Don't make it too tight, because the glue will make it fit tighter. If you need a looser fit it's easy, because both the pin width and the space between them will change automatically when you move just the one knob. You can get thousandths of an inch accuracy for exactly the fit that you are looking for.

I threw away about a dozen different shop made box joint jigs after I bought the I-Box jig. I make a lot of boxes and use the I-Box for all that I make that get box jointed corners. I use a Freud SBOX8 blade with mine most of the time. It makes nice flat bottom 1/4 and 3/8" cuts. I also have a Freud Ripping blade with an FTG (Flat Tooth Grind) that makes great 1/8" flat bottomed cuts. I have only used my I-Box to make one wider joint using my DADO blade set and it did fine as well, but not quite a perfect flat cut although this isn't as noticeable with the larger box joints. Attached are a few photos of a box to hold my I-Box jig. It was made from 1/2" Baltic Birch with 1/4" Baltic Birch top and bottom. The inside partitions are various sizes of Baltic Birch. Notice how tight and splinter free the box joint is. It's easy with the I-Box jig.

A Tip - When you get your I-Box jig, get a 2' X 4' Handi Panel of 1/4" MDF from Home Depot and make yourself a bunch of the sacrificial strips to fit the jig by copying the original They are easy to make. Just cut to size and then set up your drill press with stops to position the first hole. Drill it, then flip the piece over and drill the second hole. Then flip the piece end to end and do the same to make the two additional holes. The strips are held in place in the jig with flat heat screws, so countersink all four of the holes from the smooth side of each piece. You will get about 14 sacrificial strips this way, for a cost of about $5.50 and a half hour's time. Incra sells a package of three of these for $10 plus shipping.

Every time that I'm finished adjusting the I-Box jig for a new joint, I move the sacrificial strip left or right to a new uncut area of the sacrificial strip. When the bottom edge is used up, you can flip it over and use the top edge, when it is used up, then you will need a new sacrificial piece The sacrificial strip with the fresh position gets cut when you make the first cut of the joint, but then prevents tear out while making the rest of that size box joint. Eventually, you will need these replacement sacrificial strips, so making a bunch ahead of time for just a few bucks will save you in the long run. I'm now on my fourth since getting the I-Box jig.

Charley

[Jim Becker]

I saw a post on Facebook recently that shows a box or boxes made using that particular jig...it does really nice work.

[Mike Manning]

The I-Box jig is easy to set up for either a table saw or router table, if they have the industry standard 3/8 X 3/4 miter slot. There are adjustments to remove any side play, which is very important for accurate box joints, but the miter slot needs to be pretty close to the standard size for these adjustments to work. Setting the jig for a given size box joint is easy and very accurate, which is what makes this jig much nicer than any other on the market. You turn one knob to move the pin fingers over until the pin nearest the blade just kisses the blade. Then you turn the other knob to spread the fingers to the width of the cuts that you want, As you do this the jig is automatically setting the pin width. When set, turn the knob on the top of the I-Box to lock the settings. You should be done with the I-Box calibration. Make a test cut to be sure of the pin width and spacing, or a do test joint to be sure that a whole joint fits together well and you are. ready to go. Don't make it too tight, because the glue will make it fit tighter. If you need a looser fit it's easy, because both the pin width and the space between them will change automatically when you move just the one knob. You can get thousandths of an inch accuracy for exactly the fit that you are looking for.
Charley

I've got a couple of Delta table saws so the miter slot is standard. I briefly looked through the Incra I-Box manual online and saw mentioned just touching the blade with the pin fingers. I don't see mentioned backing off of that. I assume that must be done to avoid getting the saw blade into the metal pin. ???


I threw away about a dozen different shop made box joint jigs after I bought the I-Box jig. I make a lot of boxes and use the I-Box for all that I make that get box jointed corners. I use a Freud SBOX8 blade with mine most of the time. It makes nice flat bottom 1/4 and 3/8" cuts. I also have a Freud Ripping blade with an FTG (Flat Tooth Grind) that makes great 1/8" flat bottomed cuts. I have only used my I-Box to make one wider joint using my DADO blade set and it did fine as well, but not quite a perfect flat cut although this isn't as noticeable with the larger box joints. Attached are a few photos of a box to hold my I-Box jig. It was made from 1/2" Baltic Birch with 1/4" Baltic Birch top and bottom. The inside partitions are various sizes of Baltic Birch. Notice how tight and splinter free the box joint is. It's easy with the I-Box jig.Charley

I've got a Freud 8" Super Dado set (SD508) that I plan to continue using. It seems to cut perfectly flat joints for me. I believe I read in the manual that you can make up to 7/8" box joints with the Incra I-Box jig. That jive with what you've experienced?


A Tip - When you get your I-Box jig, get a 2' X 4' Handi Panel of 1/4" MDF from Home Depot and make yourself a bunch of the sacrificial strips to fit the jig by copying the original They are easy to make. Just cut to size and then set up your drill press with stops to position the first hole. Drill it, then flip the piece over and drill the second hole. Then flip the piece end to end and do the same to make the two additional holes. The strips are held in place in the jig with flat heat screws, so countersink all four of the holes from the smooth side of each piece. You will get about 14 sacrificial strips this way, for a cost of about $5.50 and a half hour's time. Incra sells a package of three of these for $10 plus shipping. Charley

For clarification, you change the sacrificial strip when you're changing to a different size box joint? I guess I'm trying to say that if I made half a dozen boxes with a 3/8" box joint and set the I-Box jig aside but wanted to make more 3/8" box joints during the summer I wouldn't need to change/move the sac strip would I? I re-reading the first line of the next paragraph I see clearly now you said "Every time that I'm finished adjust the I-Box jig for a NEW joint...". So only when you're going to a new size box joint. That's what I'd expect. :-)


Every time that I'm finished adjusting the I-Box jig for a new joint, I move the sacrificial strip left or right to a new uncut area of the sacrificial strip. When the bottom edge is used up, you can flip it over and use the top edge, when it is used up, then you will need a new sacrificial piece The sacrificial strip with the fresh position gets cut when you make the first cut of the joint, but then prevents tear out while making the rest of that size box joint. Eventually, you will need these replacement sacrificial strips, so making a bunch ahead of time for just a few bucks will save you in the long run. I'm now on my fourth since getting the I-Box jig.

Charley

I saw on their website they are pretty proud of their 1/4" Masonite sacrificial strips! I appreciate the tip on making a bunch before I get started. I will definitely do that.

The jig I'm going to look at is not supposed to have had that much use (a couple of times per the owner) but there are parts missing (bolts, screws, washers and a nut) which I'll have to replace if I buy it. Price is pretty good and after everyone's feedback I'm leaning toward buying it.

Thanks everyone for the feedback!

Mike

[Charles Lent]

I also have a Unisaw and prefer using it with my I-Box jig. The jig adjustment to get the miter slot bar to fit without play spreads the miter bar to remove any play in the slot, yet still allow you to slide the bar in the slot. It works very well and is a "one time" setup adjustment. You may need to change it if you ever want to use the I-Box on another saw or a router table. it's best to use the miter slot on the arbor flange side of the blade as the blade will be tightened against this arbor flange and be in the same position every time that it is installed. The directions tell you to do this.

There are two knobs for adjusting the I-Box. It's a knob within a knob kind of thing. You adjust the silver center knob to get the fingers to just lightly touch a tooth of the blade or router bit. You should be able to hear it rub as you move the blade, but should not catch on the edge of the tooth when you move the tooth away and then back. It sounds harder than it is to do.

The outer red knob is then turned to set the pin width and spacing. Set width of the cut and the pin width changes automatically. If the joint is too tight or too loose, just make slight adjustments with this red knob and make another test joint in scrap.

A third knob up on top of the jig is a lock to keep your adjustments from changing. Loosen it to make a change, but don't forget to tighten it after the change.

The next adjustment is the saw blade height. It needs to be as high as the thickness of the boards, plus the base thickness of the jig, plus about 1/32". It's easy to trim off excess length pins after the joint is assembled, but it's very hard to correct the appearance of them if they turn out to be too short. A test cut will prove that you have the blade height adequate. Make sure you lock the blade height too.

Once you have made all of these adjustments and are happy with the test joint fit, then re-position the sacrificial MDF backer so the first cut of your keeper box joint will cut a clean hole through this backer. Much like a zero clearance insert in your table saw, the close fit of the sacrificial backer around the blade cut will reduce and almost completely eliminate back side splintering and chipping of the box joint. Cutting the joint at a moderate speed with each pass over the blade will also help. If you had already used a spot on the sacrificial backer for a smaller box joint and then wanted to cut a larger box joint, you could probably use the same sacrificial strip position, but I now have plenty of new backer strips and they are cheap, so I don;t try to over think this, and just use a new uncut position each time. You should be able to make about 20 different box joint setups with one backer strip before you need a new one, so it just isn't worth the gamble, Use a new spot and get clean cut box joints.

I use my DADO blade for wider box joints, and it does well, but it does not produce a perfectly flat bottom. This is not noticeable with larger box joints like in 3/4 thick plywood or boards, but the Freud SBOX8 is much better for doing the smaller 1/4 and 3/8" box joints where non perfect bottoms of the cuts will show up more. It will depend a lot on the size of your work and how perfect you are trying to cut the joints. I used my DADO blade when I first started, then bought the SBOX8 when I wanted cleaner bottoms on the smaller joints. I recently purchased a Freud ripping blade that has the FTG tooth grind to make 1/8" (actually 0.126") box joints with nice clean and flat bottoms. This is the bottom end of the I-Box jig's capability, and mine required removal of some burrs on the fingers to get them close enough together for me to make the 1/8" box joints.

If buying a used I-Box jig, I would be concerned with the quality of the threads of the internal mechanisms and whether they had made adjustments without loosening the lock knob. You should also look at the area where the saw blade passes through to see it they cut the ends of the movable aluminum bottom pieces or the brown fiber blocks on the front and rear of the jig, both have blade clearance notches in their bottom, but fresh saw cuts should be easy to see. The plastic blade guard should be there and in good shape too. Missing bolts are easy to replace, but some of the aluminum parts and internal parts could be expensive. If anything is damaged, I would want a much better price because of it.

I actually made a duplicate of this plastic (actually Lexan) guard for the back side of the jig, since the saw blade does come out of the back side of the jig if you push the jig too far, and I used some of the anchor screws that have wood screw threads on one end and machine screw threads on the other. I replaced the safety cover screws with these front and back, and now attach both blade covers using washers and wing nuts, so I can make the jig a little smaller to fit in the box that I made to keep my I-Box in.

The inventor of the I-Box jig is a member here and I know him. He has always been willing to help anyone with I-Box problems and I kind of expected him to respond to this post by now, but Incra should be able to sell you replacement parts if you need them.

Charley

[Mike Manning]

Thanks for the feedback Charley! I like your I-Box box!

[Eric Commarato]

Love this box Charley...Very nice

[Robert Engel]

It works but you have to be familiar with the setup.

I don't use mine much so every time I have to get the manual out (but that's me).

I think if you only do them once in a while, the simple dedicated jigs are cheaper and work just as well.

[Bruce Wrenn]

Alan Schaffter, inventor of I-Box is a regular here. Email him with any questions.

[Hank Mayberry]

I saw a photo of the I-Box with a 90 deg small plastic fitting (like the D.C elbows but smaller) to plug in a shop vac for dust collection. I have the I-Box and would like to add this. Anybody know where I can buy the fitting?

[Randy Heinemann]

I've had it for awhile and used it a couple of times. It's fairly easy to setup and use. If you don't use it for awhile you most likely will need to reread the instructions or view the video.

The one box joint that the jig seems to have problems with is the Center Keyed Box Joint. It's a box joint which, by design, is intended to result in the center key to be slightly wider than the outer ones. In theory, it should be a simple joint and actually more attractive than just a simple box joint. However, in practice, it is so sensitive to even insignificant differences in wood width that it is impractical to make. I've discussed this with Incra support and even they don't seem to make it work perfectly for that joint.

Standard box joints are very easy to to do and come out essentially perfect following Incra's directions. I use it on my router table (instead of the table saw) and it works well there.

[Carl Beckett]

I have an I-box and like it. It does exactly what it was designed to do, and I didnt find it particular difficult or finicky to setup. (I use it with a dado in the TS, all the way down to single blade width fingers)

[Nick Decker]

I use mine on the router table and love it. Incra sells all the parts you might need, and I'd be surprised if they were unreasonably priced.

There are videos on You Tube that are the same as the ones Incra supplies on DVD, and they cover setup for both table saw and router table. Not hard at all, you just need to follow instructions.

[Robert Engel]

I bought one because of one project, but don't use it that often. Once you get the technique down its a good device, but honestly, not really necessary if you are capable of making your own.

The setup didn't go like the directions indicate, at least for me.

One thing I figured out was to start by setting the pins about .005 wider than the blade. Then its a matter of dialing in the pin-to-blade distance.

[J. Greg Jones]

I saw a photo of the I-Box with a 90 deg small plastic fitting (like the D.C elbows but smaller) to plug in a shop vac for dust collection. I have the I-Box and would like to add this. Anybody know where I can buy the fitting?
Can't help you with the DC fitting, but you may want to ask your question in a new thread. Seems like all the replies since you first posted yesterday are responding to the original post from 2017.

[Nick Decker]

Ha! I thought the pictures of that box posted earlier looked familiar.

[JimT Thompson]

Finally got around to making boxes and investing in the iBox jig. Read all the forums and watched the videos. Takes practice. Some key tips: treat it gently and precisely. Don’t over-tighten any of the screws. Be systematic. If the fingers are too wide or narrow after cutting a practice pair, gently adjust the finger width with the silver screw. Cut another pair. My first setup had fingers wider than the cut. Adjusted 2/2000 at a time and could see the fit improving each step. That was the penny-dropping bit for me. Took a few practice pairs but got it dialled in perfectly. This thing is not for those who rush. Very satisfying when I got it dialled in.

[Bill Sutherland]

I love mine. Have to get back making some more boxes so havent used it for some time.